Until now, an industrial electric dust collector has been used to purify air in a factory by sucking dust-containing air generated by processing machines such as a machining center and the like. Such an electric dust collector has a charging device for charging particles, such as dust, mist or the like, in dust-containing air by using corona discharge generated by applying a high voltage.
As this type of charging device, for instance, as disclosed in patent literature 1, a charging device which includes a first charging part based on a collision charging system having a first discharging electrode and a first opposite electrode, and a second charging part based on a diffusion charging system having a second discharging electrode and a second opposite electrode and arranged downstream from the first charging part is known.
Further, as disclosed in patent literature 2, an electric dust collector which uses multiple discharging electrode plates placed between two dust collecting electrode plates is also known.